support "sideload over ADB" mode

Rather than depending on the existence of some place to store a file
that is accessible to users on an an unbootable device (eg, a physical
sdcard, external USB drive, etc.), add support for sideloading
packages sent to the device with adb.

This change adds a "minimal adbd" which supports nothing but receiving
a package over adb (with the "adb sideload" command) and storing it to
a fixed filename in the /tmp ramdisk, from where it can be verified
and sideloaded in the usual way.  This should be leave available even
on locked user-build devices.

The user can select "apply package from ADB" from the recovery menu,
which starts minimal-adb mode (shutting down any real adbd that may be
running).  Once minimal-adb has received a package it exits
(restarting real adbd if appropriate) and then verification and
installation of the received package proceeds.

Change-Id: I6fe13161ca064a98d06fa32104e1f432826582f5

1 files changed, 27 insertions, 0 deletions

diff --git a/minadbd/README.txt b/minadbd/README.txt
new file mode 100644
index 0000000..0c190d0
--- /dev/null
+++ b/minadbd/README.txt
@@ -0,0 +1,27 @@
+The contents of this directory are copied from system/core/adb, with
+the following changes:
+
+adb.c
+  - much support for host mode and non-linux OS's stripped out; this
+    version only runs as adbd on the device.
+  - does not setuid/setgid itself (always stays root)
+  - only uses USB transport
+  - references to JDWP removed
+  - main() removed
+
+adb.h
+  - minor changes to match adb.c changes
+
+sockets.c
+  - references to JDWP removed
+
+services.c
+  - all services except echo_service (which is commented out) removed
+  - all host mode support removed
+  - sideload_service() added; this is the only service supported.  It
+    receives a single blob of data, writes it to a fixed filename, and
+    makes the process exit.
+
+Android.mk
+  - only builds in adbd mode; builds as static library instead of a
+    standalone executable.